Electrochemical sensor

• US 7,615,139 B2
• Filed: 11/08/2005
• Issued: 11/10/2009
• Est. Priority Date: 12/23/2004
• Status: Active Grant

• Current Assignee: Draeger Safety Incorporated (Dragerwerk AG)
• Original Assignee: Draeger Safety Incorporated (Dragerwerk AG)
• Inventors: Sommer, Sabrina, Kiesele, Herbert, Mett, Frank
• Primary Examiner(s): Sines; Brian J
• Assistant Examiner(s): DIETERLE, JENNIFER M
• Application Number:
  US11/269,184
• Publication Number:
  US 20060237313A1
• Time in Patent Office: 1,463 Days
• Field of Search: 204/411, 204/412, 204/450, 204/415, 204/406, 204/431, 204/432, 204/435, 205/775
• US Class Current: 204/412
• CPC Class Codes: G01N 27/404 Cells with anode, cathode and cell electrolyte on the same side of a permeable membrane which separates them from the sample fluid , e.g. Clark-type oxygen sensors

Abstract

An electrochemical sensor with at least one measuring electrode (3), at least one auxiliary electrode (7) and at least one reference electrode (5), wherein a protective electrode (6), which ensures at the reference electrode (5) the at least partial shielding of the reference electrode (5) against substances that would lead to a change in the reference potential when reaching the reference electrode (5), is arranged in the vicinity of the reference electrode (5). A highly stable reference potential can be obtained with the present invention.

Claims

1. An electrochemical sensor, comprising:

a housing body with an opening;

a diffusion membrane covering said opening;

an electrolyte in said housing body;

a measuring electrode in said housing body adjacent to said opening and in contact with said electrolyte;

a reference electrode consisting of a carbon containing material, said reference electrode being in said housing body in contact with said electrolyte;

a protective electrode in said housing body in contact with said electrolyte and arranged adjacent to said reference electrode at least partially surrounding said reference electrode for shielding said reference electrode against substances that would lead to a change in a reference potential when reaching said reference electrode;

an auxiliary electrode;

a mediator material in said housing body for essentially determining an electrical potential of said reference electrode; and

a sensor circuit connected to each of said measuring electrode, said reference electrode, said protective electrode and said auxiliary electrode for setting said measuring electrode at one of settable potentials and for setting the protective electrode at one of settable potentials and for determining a voltage difference between said measuring electrode and said reference electrode, for determining a voltage difference between said protective electrode and said reference electrode, and for determining a current flow through said measuring electrode and through said protective electrode, and including a microcontroller for setting said settable potentials and for receiving signals representing each said determined voltage difference and said current flow.

2. An electrochemical sensor in accordance with claim 1,

wherein said protective electrode is at a potential that deviates from a potential at which said measuring electrode is maintained by at most +/−

100 mV.

3. An electrochemical sensor in accordance with claim 1, wherein a surface of said reference electrode is partially covered with a material that has a barrier action against substances that would lead to a change in a reference potential when reaching said reference electrode.

4. An electrochemical sensor in accordance with claim 1, wherein said reference electrode is located on a plastic carrier, which seals said reference electrode on at least one side.

5. An electrochemical sensor in accordance with claim 1, wherein said reference electrode is further shielded at least partially by an ion exchange membrane.

6. An electrochemical sensor in accordance with claim 1, wherein said reference electrode is surrounded essentially by said protective electrode that is permeable to electrolyte.

7. An electrochemical sensor in accordance with claim 1, wherein the sensor is designed as a flat sensor with nearly two-dimensional diffusion paths, said protective electrode being placed such that it blocks the diffusion paths to said reference electrode for substances affecting the reference potential.

8. An electrochemical sensor in accordance with claim 1, wherein at least one layer of nonwoven material, which ensures the flat contact of both electrodes with the electrolyte, is arranged between said protective electrode and said reference electrode.

9. An electrochemical sensor in accordance with claim 1, wherein said reference electrode consists essentially of a catalytically active precious metal.

10. An electrochemical sensor in accordance with claim 1, wherein said reference electrode consists essentially of diamond-like carbon.

11. An electrochemical sensor in accordance with claim 1, wherein said reference electrode consists essentially of doped diamond.

12. An electrochemical sensor in accordance with claim 1, wherein said reference electrode consists essentially of “

carbon nanotubes.”

13. An electrochemical sensor in accordance with claim 1, wherein said protective electrode consists essentially of platinum.

14. An electrochemical sensor in accordance with claim 1, wherein said measuring electrode and said reference electrode consist essentially of the same material or materials.

15. An electrochemical sensor in accordance with claim 1, wherein said reference electrode and said protective electrode together form a sandwich structure comprising a layer of the material of the reference electrode surrounded by nonwoven material including a layer of a nonwoven material above the reference electrode and a layer of nonwoven material below the reference electrode and the protective electrode is arranged folded-over around the reference electrode and layers of nonwoven material in the form of a pocket having an open end, open to the electrolyte and with the nonwoven material in contact with said electrolyte.

16. An electrochemical sensor in accordance with claim 1, wherein:

said reference electrode and said protective electrode together form a sandwich structure comprising a layer of the material of the reference electrode surrounded by nonwoven material including a layer of a nonwoven material above the reference electrode and a layer of nonwoven material below the reference electrode and the protective electrode is arranged folded-over around the reference electrode and layers of non woven material in the form of a pocket having an open end, open to the electrolyte and with the non woven material in contact with said electrolyte; and

said microcontroller and said sensor circuit set said protective electrode at a potential that deviates from a potential at which said measuring electrode is maintained by at most +/−

100 mV.